UNFATHOMABLE: Marina Krim (above with her children) had given nanny Yoselyn Ortega more work hours to help her with money troubles.

The deranged nanny who allegedly butchered two adorable young children entrusted to her care was unraveling in recent months — suffering from mental, physical and financial issues, neighbors and police sources said yesterday.

Yoselyn Ortega, 50, appeared sick and gaunt, her Hamilton Heights neighbors said, and she appeared “nervous.”

“She lost a lot of weight. She looked very unhealthy. It looked like she was going through some problems,” said Ruben Diaz, 49. “She had aged a lot — like seven years in a few months.”

“She snapped,” said Celia Ortega, the nanny’s sister. “We don’t understand what happened to her mind.”

Still, neighbors were shocked that she was suspected of stabbing to death little Lucia Krim, 6, and her baby brother Leo, 2, on Thursday before slashing her own wrists and throat in the kids’ West 75th Street apartment.

NYPD detectives were unable to interrogate her yesterday, as she remained in a medically induced coma at New York Hospital.

Law-enforcement sources said Ortega, a Dominican who has been a US citizen for 10 years, complained of money troubles, and her employers, Marina and Kevin Krim, had given her more hours of work.

They even hooked her up with a family they knew for a baby-sitting job on the side — but the family turned her down after an interview because she was, “a little too grumpy,” a law-enforcement source said.

But nobody could predict the horror she would allegedly inflict.

Marina Krim, 36, had taken daughter Nessie, 3, to a swimming lesson but returned to her tony prewar building shortly after 5:30 p.m. because the nanny never showed up with the two other children to meet them for Lucia’s dance class, a source said.

“She got a call from the nanny saying she’d picked them up from school and she was taking them straight home,” said an employee at the Upper West Side swim and dance facility. “She [Marina] didn’t seem nervous at all; she waved to me.”

A neighbor who likely was the last to see the children alive said Lucia seemed happy in the elevator only 30 minutes before the unspeakable crime.

“She [Lucia] looked so delightful,” said upstairs neighbor Charlotte Friedman. “I said, ‘What did you do?’ and she said, ‘Dancing.’ And that was it.”

Friedman described the girl as “happy, happy, happy.”

That all changed inside the apartment. Ortega used two kitchen knives in her alleged attack on the helpless children, sources said. Lucia suffered defensive wounds from bravely trying to fight her off.

She was stabbed multiple times in the stomach and neck, and Leo was stabbed twice in the neck, the sources said.

“They both suffered. They bled out,” said a source. “The little girl tried to protect herself.”

When their unsuspecting mom arrived home a short time later, she walked into the bathroom and found her babies lying in the tub fully clothed with stab wounds on their bodies.

Ortega slashed her own throat right in front of the horrified woman, said Police Commissioner Ray Kelly.

Marina was later seen in the mezzanine of the La Rochelle building, clutching her surviving middle child, Nessie.

“She was bent over the child, screaming and holding onto the only live child she still had,” said Friedman. “They were very deep, dark screams.

“She was screaming things like, ‘I’ll never speak to her again,’ repeating that over and over again. Then screaming things like, ‘It’s all right, you’ll be all right, you’ll be all right,’ ” said neighbor Rima Starr, 63.

“Then she would get waves of the reality of what just happened and then she’d go into just plain, bloodcurdling screams, with her arms flailing out to the sides.

Marina was rushed to St. Luke’s Hospital, and when cops arrived, the hysterical woman said, “What are we going to do now? I’ll never go back there again,” law-enforcement sources said. “They can have everything. I don’t want anything.”

Marina left the hospital and was holed up with Kevin, 37, and relatives at a luxury Manhattan hotel, sources said.

There was no clear motive yesterday, although Friedman, the neighbor, said Ortega was often aloof.

“The nanny just smiled — and nothing,” she said of the elevator encounter. “She was a colder type [than] most nannies I have encountered,” Friedman said.

Ortega’s tearful sister, Celia Ortega, of The Bronx, nannied for a girl in the same ballet class as the Krim girls and recommended her sister for a job with the Krim family.

Celia said she would tell Marina, “I’d give you my life,” if it would bring back the children.

Yoselyn Ortega was under guard at the hospital. A toxicology report came back negative for drugs, sources said.

Yoselyn’s son, a 17-year-old who attends the Bronx Catholic school Mount St. Michael Academy, is staying with another aunt.

The Krims’ extended family in California was still reeling from the news.

“Who would do that to innocent children?” said Karen Krim, Kevin’s mother.